SoftSheen.Carson recommends a child be at least five years of age before applying a relaxer. Try using Beautiful Beginnings No MistakeTM No-Lye Children's Relaxer System for kids.
They even caution against pulling hair too tight.
Shampoo and condition hair weekly or bi-weekly and keep hair soft with moisturizers. Avoid pulling hair too tight when styling (i.e. braids, rubber bands, etc.) Beautiful Beginnings and Baby Love hair care products are formulated especially for kids. Try Beautiful Beginnings Conditioning Shampoo Plus Detangler, Oil Moisturizer Plus Detangler, Leave-In Conditioner Plus Detangler, Scalp Conditioner & Hairdress, and Kid's Cholesterol Gentle Conditioning Treatment.
My only solace is that she is alone. The entire rest of the class is chemical free and beautifully braided weekly. :)